Many types of power amplifiers require the outputs of multiple power modules be combined in order to achieve output power goals. In order to maximize amplifier output power, each of the combined power modules is required to have similar insertion phase. The insertion phase varies due to both transistor parameters and matching network variations.
Presently, a module's insertion phase is most often tuned in a factory environment during manufacture. This is accomplished using a variable shorted stub and variable open stub which are separated by a quarter wavelength in a power module's input matching circuitry. Decreasing the open stub's length increases insertion phase. Conversely, increasing the shorted stub's length decreases insertion phase. However, both of these variable length stubs are part of the input matching circuitry. Depending on the manner in which they are used, they may significantly vary other critical module parameters such as input return loss. This requires lengthy and cumbersome tuning algorithms in the factory to iterate towards a simultaneous solution to compensate for changes in both insertion phase and input return loss.
Therefore the need exists for a method by which a power amplifier module may be easily tuned for the proper insertion phase. The method should be easy to implement and should not affect other critical parameters of the power amplifier module.